Traditional sights include mechanical sights and optical sights. The mechanical sight refers to the metal sight, comprising a rear sight, a front sight and a notch, to assist aiming. The optical sight produces images using optical lens, with the target image and the line of sight superimposed on a same focal plane. Slight eye offset does not affect the aiming point.
In the shooting process, both two traditional sights need to calibrate the reticle and the point of impact repeatedly, so that the point of impact and the reticle center coincide with each other, which requires repeatedly adjusting the knob, or other mechanical parts. After long-term use, either the knob or other mechanical parts will be worn, resulting in error. However, long-range shooting demands high-level of aiming accuracy. A slight sight error will cause great variation on shooting results. The shortcoming is extremely inconvenient in practical applications.
A number of new technologies related to sights have been developed to help users to precisely aim. For example, when users hunt or shoot at night, the night vision function can be applied on sights, helping the users to search for objects more accurately, to shoot more easily. Currently available sights with night vision capabilities mostly include at least one objective lens, an optical enhancement device and an eyepiece lens. The objective lens forms an image of the external scenery on the entrance window of the optical enhancement device. The optical enhancement device increases the brightness of the images and display the same, enhancing the night vision capability. However, the increasing brightness from background to targeted object leads to decreased distinction in brightness between the boundary of targeted object image and background. As a result, the boundary of night image is blurred. Shooters can only obtain the position and orientation of the targeted object, as opposed to the best aiming point. They have to rely on their own experience to determine the best aiming point, which is hard to achieve and instable in shooting accuracy.
Currently available sights have a magnification adjustment function to switch magnification, helping users to observe targeted object clearly and improve shooting accuracy. Most of the magnification adjustment functions can only be achieved manually. However, in shooting practice, users have to manually twist the magnification adjustment ring continuously. Either the hand holding the butt of the gun or the other hand holding the trigger has to be freed up to operate the magnification adjustment ring. As such, aiming and shooting actions cannot be achieved simultaneously, affecting shooting accuracy.
When a sight is attached to the barrel of a firearm for the first time, the barrel needs to calibrated or zeroed, which is usually done by trial and correction. For example, one person at a known distance to the target can launch one or more bullets. Then determine the offset between the landed bullet and the location originally targeted. Then make sight adjustments to eliminate bias. Repeat the whole process until the bullet hole and the original targeted location coincide with each other. However, new calibration has to be performed before the actual hunting or other applications as the initial calibration was done in a particular environment. In the actual hunting process, the actual environmental factors, including temperature, pressure, humidity, wind speed and direction will apply friction on bullets, affecting the trajectory of ballistic. Furthermore, the targeted object is usually at a different distance compared to the distance of the initial calibration. In the process of calibration, after launching a bullet, it is common that the bullet is off target or the point of impact cannot be found on the display of the sight. It's a waste of time and bullets. Experienced users can rely on shooting experience to perform initial calibration, but beginners usually have no clue at all.